How do you create grass?
This can be done with a Hair particle system.


Add a hair particle system to your mesh:


If you want to simulate the hair dynamics with realistic wind, you can use a Smoke simulation:


Add a smoke domain object and a Smoke Flow object
Add a Wind force field and a Turbulence force field (ShiftAAdd > Force field)
Adjust the settings until you have a nice simulation (optionally add some collision objects) and bake the smoke
Disable the Wind and Turbulence force fields for the particle system in Particles > Field Weights:


Add a Smoke Flow force field and select the smoke domain object for the domain.
Enable Dynamics in the particle system and increase the Stiffness
Bake the particles, then hide the smoke domain and emitter:





As for the color variation, you could use a Procedural texture:



Result: